“It’s terrible,” Chief Sheridan said on Monday afternoon. “We are seeing something in this country that we have never seen before.”

Fifty-five law enforcement officers have been killed nationwide so far in 2018, a slight increase from the same period last year, according to the National Law Enforcement Officers Memorial Fund, which tracks officer fatalities. In all of 2017, 129 officers were killed on duty, the second-lowest yearly total in the past six decades, according to the same group.

Residents on Linwen Way in Perry Hall said the episode started when a neighbor spotted four men walking behind a home on the block. That neighbor called 911 to report suspicious activity and then called again when she spotted the men carrying items out of the house and into a dark-colored Jeep on the street, said Tony Kurek, who lives on Linwen Way.

While three people were inside the house, Mr. Harris waited in the driver’s seat of the Jeep, according to court records. As they started to pull out of the cul-de-sac, Officer Caprio, who was on patrol, pulled up and parked her car to block the Jeep, according to Mr. Kurek, whose son Dakota was in the front yard and saw the confrontation unfold.

Her gun drawn, the officer stepped out of her car and ordered the men to exit the Jeep, Mr. Kurek said.

“They hit the throttle and went at her,” Mr. Kurek said in an interview on Tuesday. “The path that they took was right through her and they drove right over and out of the neighborhood.”