Orlando police said Thursday that they believe the four children found dead following a 21-hour standoff were fatally shot at the beginning of the hostage situation.

According to the Orlando Sentinel, the Orlando Police Department (OPD) suspects that Gary Wayne Lindsey Jr., 35, had killed Irayan Pluth, 11, Lillia Pluth, 10, Aidan Lindsey, 6, and Dove Lindsey, 1, shortly after starting a gunfight around midnight on Sunday. Police said the children were in their respective beds and wearing their pajamas when they were found—leading detectives to believe the children were sleeping when they were killed, according to Orlando Weekly.

“Based on the condition of the victims’ bodies at the time of discovery, coupled with a thorough review of the investigation so far regarding the case, OPD homicide detectives believe the children were killed while they slept, either shortly before or shortly after the suspect’s initial contact with OPD officers,” the agency said in a statement.

Police were called to the Orlando home following reports that Lindsey had battered his girlfriend and child’s mother, Ciara López, 31. Lindsey is the father of Aidan and Dove.

As CrimeOnline previously reported, Lindsey is said to have critically wounded officer Kevin Valencia before barricading himself in the home.

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Authorities reportedly spent 21 hours trying to reach a peaceful resolution with Lindsey, which would entail him surrendering the four children.

It was around 9 p.m. Monday when a SWAT team entered the home after officers saw one child dead inside. Police then discovered Lindsey turned the gun on himself.

OPD Chief John Mina told reporters Tuesday that couldn’t specify when the four children were killed. He went on to say there was “never any indication” the children were in jeopardy during the daylong standoff.

[Featured image: Irayan Pluth, Lillia Pluth, Aidan Lindsey, and Dove Lindsey/GoFundMe]