Matthew Marshall and Matthew L. Johnson, both 18, are charged with second-degree murder, two counts of armed criminal action, first-degree burglary and tampering with evidence. The charges were filed Tuesday afternoon by Warren County Prosecutor Mike Wright.

The two have been held on first-degree assault charges since the Jan. 1, 2009, incident.

Marshall, of the 29000 block of Marlin Drive in Wright City, and Johnson, of St. Ann, are being held on a $500,000 cash-only bond.

No court appearances have been scheduled on the new charges.

Wright said he delayed filing murder charges until he could meet with detectives after reports were submitted to his office a couple of weeks ago.

He met with detectives Tuesday morning. "I filed additional charges that I felt were appropriate," Wright told The Record.

The investigation was extended in part due to the need to reinterview witnesses since many of them were intoxicated when the alleged crime occurred.

Warren County Sheriff Kevin Harrison said many of the partygoers had to be tracked down, including one who was located in southwest Missouri.

"We had an unusual amount of witnesses from our perspective," he said. "We weren't willing to put much credibility into the initial statements. Naturally, it takes awhile to sift through."

Wright added: "We wanted to verify those stories."

The incident occurred at a home in the 13000 block of Bobwhite Lane in Wright City.

According to police, Marshall and Johnson stormed the party armed with bats and knives and forced their way into the residence.

Fernando Melgar, a 31-year-old Hispanic male from Wright City, was found dead when police responded to the scene following a 911 call at 12:51 a.m. He had been stabbed several times in the chest, abdomen and back.

A second victim, Raymond T. Post, 45, who lived at the residence, also was stabbed. He was transported by ARCH helicopter to a St. Louis hospital. He had his spleen removed, his liver was damaged and his lung punctured. He has since recovered.

Authorities have yet to identify who stabbed Melgar or Post.

Police said Marshall and Johnson showed up at the party because a female friend didn't like the way she was being treated.

Both suspects were arrested later in the morning at two separate locations. Harrison said Johnson was taken into custody by St. Peters police on Interstate 70 near the Fifth Street exit in St. Charles. Marshall was apprehended near Houston, Mo., located a couple of hours south, en route to West Plains.

According to court documents, Marshall and Johnson disposed of the three knives by throwing them from a vehicle near the 199-mile marker on eastbound Interstate 70. Police did not say if the weapons were recovered.