A mother and her three children have been gunned down in a Florida apartment in a "senseless" mass shooting, according to authorities.

On Tuesday night, after family members called 911, officers responded to the Sunrise Apartments and found a mother, her son and two daughters shot dead, said Lake Wales police.

The victims were ages 40, 21, 17 and 11, according to police.

Al Stenson, who knew the victims, allegedly shot them in the apartment around 5 a.m. Tuesday and then fled, according to police.

The motive is unknown, police said.

"Completely senseless. It makes absolutely no sense," Lake Wales Police Chief Chris Velasquez said at a news conference.

Stenson, 38, is wanted on four counts of first-degree murder, police said, adding that authorities have "located" him and "are actively working to take him into custody."

Police said there's no threat to the public.

ABC News' Robinson Perez contributed to this report.