A black woman who was holding her five-year-old son was shot and killed by police in Randallstown, Maryland, on Monday afternoon after an extended standoff.

The 23-year-old Korryn Gaines allegedly pointed a shotgun at officers and said: “If you don’t leave, I’m going to kill you.” Authorities said that officers then fired and Gaines returned fire, but did not strike any police. The five-year-old boy injured a limb during the firefight but it was not initially clear whether bullets from police or Gaines struck him. The injuries were not believed to be life-threatening.

“We discharged one round at her,” police chief James Johnson told reporters at an evening news conference. “In return, she fired several rounds back at us. We fired again at her, striking and killing her.”

Facebook Twitter Pinterest Korryn Gaines Photograph: facebook image

The standoff began after three officers went to Gaines’ apartment in the Baltimore suburb to serve arrest warrants on her and a man, according to police. Gaines was wanted for failing to appear in court on traffic charges dating from a stop in March and the man was wanted for assault, authorities said.

One officer got a key from the landlord and opened the apartment after no one responded to repeated knocks. The officer saw Gaines sitting on the floor, pointing the gun at him, police said. The officers retreated to the hallway, and a man ran from the apartment with a one-year-old boy, authorities said. That man was arrested.

Police said that negotiators tried to talk with Gaines and that she repeatedly refused to surrender. Authorities said that as of this morning they did not know whether any of the officers involved were wearing body cameras.

According to court records, Gaines’ bench warrant stemmed from an array of traffic charges, including disorderly conduct and resisting arrest. Gaines was charged after a traffic stop last March.

The department did not give the races of the officers involved, who were placed on routine administrative leave. Their names will be released 48 hours after the incident, in accordance with the department’s contract with the Fraternal Order of Police.

Videos posted on Gaines’ Instagram page appear to have been taken during the standoff. In one, Gaines can be heard asking her son who is outside and the boy responds: “The police”. Gaines then asks “and what are they trying to do?” And the boy replies: “They’re trying to kill us.”

According to the Counted, the Guardian’s ongoing investigation into police killings, Gaines is the ninth black woman to be killed by US police in 2016 and the first of the summer.

The Associated Press contributed to this report.