Mom, her 3 kids killed in 'senseless' mass shooting at apartment

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.

When authorities tracked 38-year-old Stenson to the Slumberland Motel in Sanford, "Stenson made statements that he would kill himself or force law enforcement to kill him," police said in a statement.

An hourslong standoff ended with an officer-involved shooting and Stenson was pronounced dead at the scene, police said.

ABC News' Robinson Perez contributed to this report.