"Internal affairs is looking at it in its entirety," he said. "We are pulling back the layers unequivocally to make sure there were no warning signs here."
He said the shooting of Diggs came suddenly and unexpectedly.
"They were talking to her, they were interviewing her when she was literally shot right in front of them," he said. "The window of time was very quick. … You're not expecting to go to a home of a police officer, someone you work side by side with, who engages you in a gunbattle."
He said Smith was not given any preferential treatment during the barricade.
"The minute he fired at that young lady and our police officers — he was treated as a suspect," Guglielmi said.
Guglielmi and pretrial services officials said Smith had never been charged with a crime before. He was honorably discharged from the Army in 1992, according to a statement in court Wednesday.
Smith, who worked in the motorcade unit, had tactical training and broad expertise. He was often assigned to motorcades with the Secret Service when high-profile officials came into town, Guglielmi said, and he was respected in the department.
Smith has received SWAT, aviation, traffic, tactical and motorcycle escort training.
"There was no prior history of domestic abuse that would have raised suspicion," Guglielmi said. "He was in one of the most specialized sections in the department, and that unit selects officers of extreme character, officers who are highly trained."
Police were cautious during the standoff because Smith's advanced training made him a dangerous suspect. Guglielmi said officers from Smith's own unit assisted in negotiations, as did a clinical psychologist.
Smith surrendered to police at 9:07 p.m. In an interview at the homicide unit, police say, he apologized for his actions.
Police say they recovered a gun from a bathroom in the house and found several shell casings near the second-floor bedroom window. It's not clear whether the gun was Smith's service weapon.
On Wednesday, Smith was led alone into the courtroom at the Central Booking and Intake Center shortly before 11 a.m. with his hands cuffed in front of him. He wore a bright pink shirt and dark slacks. He was led to a bench in the middle of the room where he sat breathing heavily, his eyes bloodshot.
District Judge Shannon E. Avery read Smith his rights and asked whether he had any questions.
"No, your honor," he said.
The state's attorney's office asked that Smith continue to be held without bail, and a public defender on hand for the morning's bail reviews put up no argument.
"Based on the extreme nature of the offense, I do find that the defendant is a threat to public safety," Avery said, ordering Smith held.
Baltimore Sun reporters Yvonne Wenger and Kevin Rector contributed to this article.