2/21 -- 5:51 AM PT -- Lyndell Mays was released from the hospital Tuesday evening and taken into custody ... where he took a mug shot. You can see he appeared to still have a large bandage on his face as he went through the booking process.

Police officers in Kansas City claim Lyndell Mays admitted he fired the first shots at the Chiefs' Super Bowl parade last week ... before he allegedly said he "shouldn't have done that."

According to court documents, Mays made the stunning admissions to the Kansas City Police Department on Feb. 16 -- two days after more than 20 people were struck by gunfire while celebrating Patrick Mahomes and Travis Kelce's latest championship at Union Station.

In the docs, a KCPD detective wrote that Mays was interviewed at a local hospital after suffering from an apparent gunshot wound. Initially, the docs state Mays told police he didn't shoot at anyone following a dispute with a group of individuals at the parade -- although when "Mays was confronted that we had surveillance video of the incident, he then changed his story."

Mays, according to cops, said a group he was quarreling with had told him, "I'm going to get you" ... something that Mays apparently believed meant, "I'm going to kill you."

Cops say Mays then told them he shot first -- "maybe two times." However, according to the docs, Mays said he initially hesitated to pull the trigger "because he knew there were kids there." The docs also state Mays wasn't specifically targeting anyone when he ultimately decided to fire, because "they all could have had guns."

"So he just randomly picked one of the individuals to target," cops wrote in the documents.

Cops also noted in the docs that the person Mays ended up shooting at was actually running away from him.

"When asked why Lyndell Mays advanced on them to begin with, he replied, 'Stupid, man,'" cops wrote in the documents. "'Just pulled a gun out and started shooting. I shouldn't have done that. Just being stupid.'"

Prosecutors announced Tuesday that following officers' talks with Mays, they hit him with charges of murder in the second degree, armed criminal action, and unlawful use of a weapon.

Prosecutors also revealed Tuesday a man named Dominic Miller had been hit with the same charges as well.

According to court documents, authorities spoke with Miller over his alleged role in the shooting on Feb. 16 after they say they identified through video and eyewitness statements that he was involved in the argument that preceded the gunfire.

Cops say Miller -- who was also at a local hospital recovering from apparent gunshot wounds -- initially told them he ran after hearing gunshots, and was struck in the abdomen as he was trying to hightail it away from the area. However, the docs state when authorities told them his actions were filmed on video -- he admitted to firing his Taurus G3 9mm handgun during the altercation.

According to the docs, Miller told them that after he heard gunshots, "he observed a black male with dreads armed with a black handgun shooting at him."

"Miller stated he returned fire with his own firearm," cops wrote in the docs. "Miller estimated he fired 4-5 shots and was uncertain if he struck the individual he was shooting at."

According to the docs, a .38 caliber class bullet was recovered from the body of Lisa Lopez-Galvan, who died amid the shooting. Cops say detectives later discovered the bullet was fired from the Taurus G3 9mm gun that Miller had acknowledged that he possessed and shot.

Both Miller and Mays -- who are 23 years old or younger -- are now currently being held on a $1 million bond.

Previously, prosecutors hit two juveniles with charges over their connection to the shooting as well.

Both Kelce and Mahomes, meanwhile, have offered their prayers for the victims of the shooting ... with each donating thousands to help in recovery efforts.