Witnesses described escalating threats, a shotgun confrontation and a second assault before officers reached the North Valley residence, police say.

ALBUQUERQUE, N.M. — A 64-year-old Albuquerque man faces an open count of murder and three additional felony charges after police say he fatally shot his 34-year-old son during a confrontation inside a North Valley home and then attacked the younger man’s girlfriend as she called for help.

Mark Leib was arrested in connection with the Sept. 20 death of his son, Matthew Leib, following a late-night shooting on Sabre Court NW. The case rests in large part on accounts given by Matthew Leib’s girlfriend, another friend who had been at the house and a nearby resident, along with statements police attributed to Mark Leib and physical evidence recovered from the residence. The accusations are allegations contained in police and court records and have not been established at trial.

The confrontation developed over a relatively short period after Mark Leib returned to the home, according to accounts in the criminal complaint cited by local and national news organizations. Matthew Leib was spending time at the residence with his girlfriend and another friend. Witnesses told investigators that the older Leib arrived in an agitated state and began talking about killing or hurting people. The remarks were alarming enough that Matthew Leib’s friend began preparing to leave and warned that the situation was becoming dangerous.

Matthew Leib’s girlfriend initially tried to separate Mark Leib from the others by getting him into a bedroom, according to the complaint. That effort did not end the confrontation. She told police that Leib later came back out carrying a shotgun. The Albuquerque Journal described the firearm as a double-barrel shotgun, while other reporting on the complaint described it as short-barreled. Investigators said the woman tried to move Leib away from the others, leading to a physical struggle in which he allegedly grabbed her clothing and struck her after she struck him.

Police say the danger escalated when the firearm was pointed at the woman and Mark Leib threatened to kill her. Matthew Leib then moved between his father and his girlfriend, according to the friend’s account. The two men argued, and the father allegedly threatened his son as well. The girlfriend and the friend eventually got outside and left the immediate confrontation. Their departure did not resolve the crisis: Both realized that Matthew Leib had not come out with them, prompting them to return to the home to check on him.

What they encountered on their return became a central part of the police account. The complaint says Mark Leib came outside and announced that he had shot his son. Matthew Leib’s girlfriend then went back into the house and found the 34-year-old in a hallway with gunshot wounds. She called 911 and stayed with him. Police said Mark Leib then entered the residence again and struck the woman multiple times in the back of the head with the stock of the shotgun while she was beside Matthew Leib and communicating with emergency dispatchers.

Emergency crews could not save Matthew Leib, according to the complaint. Police were dispatched to the Sabre Court area at about 11:18 p.m. after reports of a shooting. A neighbor separately told investigators that she had heard a loud gathering outside, followed by an argument and two noises she thought could have been gunshots. Those observations gave detectives another account of the disturbance even though the neighbor was not described as having witnessed the shooting itself.

Investigators also cited statements they say Mark Leib made before and after his detention. Police obtained a 911 call from a blocked or unidentified number that they believed was connected to Leib, according to reporting on the complaint. The caller repeatedly acknowledged killing his son. Officers said Leib continued making statements about the killing after he was detained. Those reported remarks are part of the prosecution’s early evidence, but their legal significance will ultimately depend on what evidence is admitted and tested as the criminal case moves forward.

When detectives later attempted to question Leib at the police station, they advised him of his rights and he declined to answer substantive questions, according to the complaint. Exercising the constitutional right to remain silent is not evidence of guilt. Investigators instead continued building the case through witness interviews, emergency calls and the physical scene. A search of the residence reportedly produced the shotgun, two spent shell casings and impacts in the hallway walls in addition to Matthew Leib’s body.

Leib was booked into the Metropolitan Detention Center and initially charged with an open count of murder, two counts of aggravated assault with a deadly weapon and one count of aggravated battery with a deadly weapon. An open murder count does not itself establish which murder theory will ultimately be submitted to a jury. New Mexico court materials recognize the use of an open count in murder prosecutions, while requiring the state to prove the elements of whatever offense is ultimately pursued. Leib is presumed innocent unless he is convicted.

The case also appears in Albuquerque Police Department homicide statistics for 2026. The department lists the Sept. 20 Sabre Court homicide as solved, a designation reflecting that investigators have identified and charged a suspect rather than a judicial finding of guilt. As of Nov. 6, APD reported 50 homicide victims in the city during 2026, with 43 of the 50 cases listed as solved. Firearms accounted for 36 of those homicide cases, according to the department’s published figures.

Those citywide figures provide context but do not answer the central unresolved questions in the Leib prosecution. Publicly available reporting reviewed for this article does not establish a motive for the fatal shooting, and the initial complaint does not amount to a finding about what occurred beyond a reasonable doubt. Witness testimony, emergency-call evidence, forensic findings and any defense evidence could become important if the case proceeds toward trial. The reports reviewed also did not identify a later public disposition resolving the charges as of Nov. 7.

The immediate record therefore remains one of accusation and investigation: Matthew Leib is dead, his girlfriend survived the alleged assault, and Mark Leib faces a murder prosecution and three related assault counts arising from the same night. Further court filings will determine how prosecutors formally present the homicide charge and what defenses are raised in response.

Author note: Last updated November 7, 2026.