Two strangers stood facing each other when the apartment door opened Monday afternoon, but Martynenez Grigsby and Courtney Vanderhorst know each other now — as alleged assailant and victim.

Grigsby, 26, was booked on a count of aggravated battery after she shot Vanderhorst, 20, in the right shoulder, according to court documents. Police previously said he was shot in the chest.

Grigsby told police that Vanderhorst forced his way inside her apartment.

Vanderhorst said he was stunned to find a stranger inside what he thought was a relative’s apartment and was shot for no reason, according to a police report.

Police said Grigsby was uncooperative with the investigation and clammed up once she was confronted with Vanderhorst’s account, which agreed with what her 9-year-old son said he saw.

Grigsby, who lives in the Marquis Apartments in the 2600 block of Poydras Street, told police she heard a knock on the door of her fourth-floor unit about 4:10 p.m.

According to court documents, she told police that she opened the door to find Vanderhorst standing there. She said she told him to leave since she didn’t know him and tried to close the door but that he pushed it opened and walked inside.

That’s when she fired a single shot at Vanderhorst, piercing his right shoulder. He was rushed to Interim LSU Hospital in critical condition.

Vanderhorst, who lives in Harvey, said he thought he was at a relative’s apartment and was unsure who Grigsby was when she opened the door.

The victim’s grandfather, Lloyd Vanderhorst, lives on the fifth floor, directly above Grigsby’s apartment. He said Sunday that he believed his grandson had accidentally tried to enter the wrong unit.

“Everything here looks the same if you don’t pay attention to the numbers,” he said.

Courtney Vanderhorst admitted to police that he pushed the door open but denied that he set foot inside. He said he stayed in the hallway.

That story is the same as what Grigsby’s son told police he saw.

According to court documents, the 9-year-old boy said his mother was already armed when she opened the door.

The boy told police that his mother told Vanderhorst to leave and “accidentally” shot him as he stood in the hall.

Police brought Grigsby to the 1st District police station to interview her about what happened. She refused to talk and requested an attorney once she was asked about the stories from her son and Vanderhorst that differed from her account, according to court records.

Grigsby remained jailed Monday afternoon with bail set at $10,000, according to jail records.

Grigsby was the second person in recent days to be arrested in New Orleans in the shooting of someone possibly committing a crime.

The Rev. Willie Littleton, 62, last Wednesday fired on two men suspected of stealing copper from an air-conditioning unit at his church in the 1200 block of Vallette Street in Algiers.

Littleton was booked with aggravated battery by shooting the next day.

Follow Danny Monteverde on Twitter, @DCMonteverde.