ALBUQUERQUE, N.M. (AP) — A lawyer for an Afghan refugee accused in the Albuquerque slayings of three Muslim entered a not guilty plea Friday on her client’s behalf.

Muhammad Syed, 51, appeared remotely for the court hearing and will remain held without bond pending trial. He is charged with three counts of murder and tampering with evidence, and police have identified him as the suspect in the killing of a fourth Muslim man.

Syed, who has been in the U.S. with his family for several years, previously denied involvement in the killings when authorities detained him earlier this month.

Authorities have not disclosed a motive for the killings, but prosecutors have described Syed as having a violent history. His public defenders have argued that previous allegations of domestic violence against Syed never resulted in convictions.

Authorities have said they have linked bullet casings found at two of the crime scenes with casings found in Syed’s vehicle and with guns found at his home and in his vehicle.

Syed was arrested Aug. 8 more than 100 miles (160 kilometers) from his Albuquerque home after tips led investigators to the Syed family. He told authorities he was on his way to Texas to find a new home for his family, saying he was concerned about the ambush-style killings.

Syed has been charged with these killings:

— Aftab Hussein, 41, was slain July 26 after parking his car in his usual spot near his home.

— Muhammad Afzaal Hussain, a 27-year-old urban planner who had worked on the campaign of a New Mexico congresswoman, was gunned down Aug. 1 while taking his evening walk.

— Naeem Hussain was shot Aug. 5 as he sat in his vehicle outside a refugee resettlement agency on the city’s south side following funeral services for two of the other shooting victims. Shots were fired at Hussain’s SUV, striking him in the head and the arm.

Federal authorities in court filings said cell phone records show Syed and his son, Shaheen Syed, were in the proximity of the Aug. 5 crime scene and it appeared from video surveillance that the elder Syed had followed Naeem Hussain.

Shaheen Syed faces a federal charge of providing a false address when purchasing a gun last year. His defense attorney has disputed that charge, but the younger Syed also remains in custody pending trial.

Muhammad Syed is the primary suspect — but hasn’t been charged — in last November’s slaying of Muhammad Zahir Ahmadi, a 62-year-old Afghan immigrant who was fatally shot in the head behind the market he owned.