Police said they arrested an elderly woman after she killed her terminally ill husband at a Daytona Beach, Fla., hospital Saturday, as part of a pact the pair made weeks beforehand.

She could be charged with first-degree murder.

“Apparently, because he was terminally ill, they had a conversation about it, and they actually planned this approximately about three weeks ago, if he continued to take a turn for the worse,” Daytona Beach Police Chief Jakari Young said at a press conference. “He wanted her to end this.”

The authorities received an alert about the shooting on the 11th floor of the AdventHealth Daytona Beach hospital around 11:45 a.m. on Saturday. After the 76-year-old woman shot her 77-year-old husband in the head, police said, hostage negotiators spoke with the woman. They spoke with her until 3 p.m., when they were able to take her into custody after using a flash-bang grenade to distract her.

The authorities said they are unsure how the woman was able to bring a gun into the hospital. The police chief said she did not threaten hospital staff or other patients.

During negotiations, the authorities learned that the original plan would involve the husband shooting both himself, and his wife, who Young described as being “in a depressed state.” However, the wife took over after they realized he was too weak to do it himself.