Alonzo Mingo, 37, is facing three counts of second-degree murder committed without premeditation but with intent after an attempted robbery turned deadly, according to the complaint filed in Anoka County, Minnesota, district court.
Authorities said Mr Mingo drove his car to a home in suburban Minneapolis where two children under the age of five were present shortly after noon on Friday, before going to the front door dressed as a UPS delivery worker.
He was then let inside the house, authorities said, and demanded money at gunpoint before shooting three people in the head.
He was accompanied by one other person dressed in a UPS uniform and a third suspect, all of whom went into the residence, prosecutors said. One of the suspects was seen carrying a cardboard box.
Police arrived at the home on Friday where they found two dead men and a dead woman.
Authorities named the deceased as 42-year-old Shannon Patricia Jungwirth, her 20-year-old son Jorge Alexander Reyes-Jungwirth, and her 39-year-old husband Mario Alberto Trejo Estrada.
Prosecutors said footage from a home camera showed Mr Mingo lead a man at gunpoint into a bedroom where a woman and two children were, before holding the man and woman at gunpoint.
Mr Mingo could then be seen leading the group from the room before returning to the bedroom with only the woman and shooting her at point-blank range, according to police.
“The older child can be seen entering the bedroom shortly thereafter, crying hysterically,” Coon Rapids police wrote in a probable cause statement.
The younger child later tried to check on the woman, but the older child pulled them away and out of the room, according to the statement.
Police arrested Mr Mingo several hours later after they found him driving the same vehicle seen in the footage leaving the property seven minutes after the attack.
The two other people seen entering the home were not found, and the criminal complaint makes no mention of charges against them. No other suspects have been named.
Coon Rapids police said they found a UPS delivery uniform top and vest in a backpack in Mr Mingo’s vehicle.
Police added Mr Mingo had been employed at UPS until early January.
UPS spokesperson Karen Tomaszewski Hill said in an email that Mr Mingo was a seasonal employee “who only worked for the company for a short time”.
“As this is an active investigation, we will defer to investigating authorities for additional questions,” she said.
Following his arrest, Mr Mingo was jailed on a $5m bond. He could face up to 40 years in prison for each murder count if he is convicted.
A potential motive for the killings was not revealed. However, the Star Tribune reported on Monday that it had obtained an affidavit connected to the investigation which alleged that Mario Alberto Trejo Estrada, one of the victims, had been selling cocaine, fentanyl and methamphetamine, resulting in cash earnings he sent to Mexico.
Authorities reportedly searched a storage unit affiliated with Mr Estrada later on Friday and turned up psilocybin mushrooms, marijuana, methamphetamine and an unspecified white powder.