A convicted felon who engaged police in a nearly daylong standoff at his Florida apartment before taking his own life fatally shot four children in their sleep at the start of the confrontation, the Orlando Police Department said on Thursday.Police who stormed the apartment after 21 hours on Monday night found suspect Gary Wayne Lindsey, 35, dead of a self-inflicted gunshot wound. The bodies of four children were also found inside the three-bedroom apartment.Police have said Lindsey was the father of the two youngest children.The incident began when Lindsey's girlfriend called police to report an incident of domestic violence. The suspect opened fire on police through a front door of the apartment, critically wounding officer Kevin Valencia. The girlfriend, who was the mother of all four children, fled and was unhurt, according to the Orlando police."Our preliminary investigation has revealed the children were found deceased lying in their respective beds, wearing the same bedtime clothes their mother reported they were dressed in when she put them to bed," the Orlando Police Department said on Twitter."Based on the condition of the victims' bodies at the time of discovery, coupled with a thorough review of the investigation so far regarding this case, OPD homicide detectives believe the children were killed while they slept, either shortly before or shortly after the suspect's initial contact with (police)," the police department said.Valencia remained in critical condition on Thursday, according to the statement posted on Twitter.