Criminal proceedings were suspended Thursday for a man charged with killing four people in a shooting at a Southern California office complex pending a mental competency evaluation, his attorney said.

Kenneth Morrison, assistant public defender, said he told the court that Aminadab Gaxiola Gonzalez was not mentally competent to assist in his own defense and might not understand the charges against him. It was the first time his client was brought to court since he was charged more than three months ago, Morrison said.

Two doctors were assigned to assess the competency of Gaxiola Gonzalez, who remains in custody and faces four counts of murder and three counts of attempted murder. The next hearing in the case is scheduled for Aug. 6.

His arraignment has been delayed since he was wounded in connection with the attack in the city of Orange.

Authorities say Gaxiola Gonzalez killed four people including a 9-year-old boy, wounded the boy’s mother and fired shots at two police officers. Authorities had to use bolt cutters to break bicycle locks that had been used to shut the complex’s gates.

Authorities have said Gaxiola Gonzalez knew the victims but they have not provided details about the relationships.