Background: The 6300 block of Parkdale Drive in Dallas, Texas (Google Maps). Inset: Jose Magareno (Dallas County Sheriff”s Department).

A man charged with killing his cousin in Texas allegedly claimed he did it to test his relative’s reaction time.

Jose Magareno, 21, is in the Dallas County Detention Center on a charge of murder, court records show.

The event reportedly happened around 5 p.m. on Monday when 19-year-old Emmanuel Najera and his younger brother visited Magareno’s house to celebrate Najera’s birthday, as detailed in an arrest affidavit accessed by The Dallas Morning News. During a conversation about guns and concealed carry, they went to Magareno’s room.

As per local Fox affiliate KDFW, Magareno handed Najera a gun, expressing a desire to “test his reaction time.” He reportedly informed the police that he attempted to unload his gun.

Magareno is suspected of shooting his younger cousin, as he called 911, claiming he “accidentally” shot Najera in the chest. Dallas Police Department officers responded to the 6300 block of Parkdale Drive in Dallas, and Najera was taken to a local hospital, where he ultimately died, as stated in a press release by the department.

The suspect was detained, and during his conversation with officers, he supposedly added more details about the accident. Magareno mentioned that he regularly practiced with his gun and thought he had removed all the bullets before firing.

Hours later, early Tuesday morning, he was booked into jail and charged with murder. The case was still being investigated as of Tuesday.