No sign of immediate threat to kids during Orlando standoff that left 4 children dead: Police

During the 21-hour hostage standoff at an Orlando apartment that left four young children shot dead, there was never any indication of an imminent threat to the kids, police said Tuesday.

It's not clear when the children died during the standoff, which lasted from Sunday night to Monday night, City of Orlando Police Chief John Mina said at a news conference Tuesday.

The standoff began after the girlfriend of suspect Gary Lindsey Jr. contacted police to report that he'd battered her, police said. She met officers outside and directed them toward the apartment.

Lindsey, armed with two rifles, two shotguns and a handgun, shot a police officer, critically injuring him, police said.

Lindsey then took four children -- ages 1, 6, 10 and 11 -- hostage, police said.

As the standoff got underway, negotiators communicated with Lindsey through social media, friends, relatives and over the phone, police said.

Lindsey eventually shot all of the children before turning a gun on himself, police said.

The standoff came to an end Monday night when officers breached several windows and saw what appeared to be a dead child, Mina said. That's when the police decided to do an explosive breach on the apartment, Mina said.

Officers deployed gas and started clearing the apartment room by room, Mina said. They found two children dead together in one bedroom and two more children dead in another room, and "based on everything I have seen" it was not police bullets that killed the children.

The injured police officer, Kevin Valencia, remained in critical condition Tuesday evening, Mina said.

Two of the children were the suspect's and two of the children were the girlfriend's.

Family members of the four children are "in shock," family friend Walter Benenati told ABC News. "I can’t imagine what they are going through."

"They are just in utter disbelief of what has occurred. I'm trying to do what I can to help out," he continued. "I'm doing what I can as a family friend [to raise] money for funeral expenses for the four children ... people in this whole community here in Orlando have been touched by this."

The coroner's office has not released the children's identities.