A former patient at a San Diego County dental office was charged with murder and attempted murder on March 5 after he opened fire at the clinic days earlier, killing one and wounding two.

Mohammed Abdulkareem, 29, of El Cajon has pleaded not guilty to both charges, according to a statement released by the District Attorney’s Office. He faces life in prison if convicted.

Abdulkareem opened fire at the dental office on Feb. 29, killing dentist Benjamin Harouni, 28, and injuring two workers, according to the statement.

Abdulkareem was a well-known former patient at the office and had shown up there multiple times during the six months prior to the attack to complain about his dental work, according to the DA’s statement.

Arguing against bail, prosecutors pointed out that the defendant fired 23 rounds in one minute from a semiautomatic handgun.

Abdulkareem fled in a rented truck but was arrested in the Balboa Park area on the evening of Feb. 29. He was found in possession of a handgun, ammunition and multiple handgun magazines, authorities said.

The DA said that on Feb. 24,  Abdulkareem purchased a handgun consistent with the shooting.

“Today is the first step in seeking justice for the victims, their families, friends, and community in this tragic case,” DA Summer Stephan said in the statement. “We grieve the loss of Dr. Benjamin Harouni along with his family.”

Authorities said that the investigation is ongoing and additional charges could be brought against Abdulkareem. He is currently held on no bail.