"Yes, he was released from custody and as far as why charges have not been filed, call the state's attorney office," Prince George's County Police spokesman Tyler Hunter said.
Efforts to reach the state's attorney for comment Saturday night were unsuccessful.
The shooting happened Friday night at the man's residence in Temple Hills, in the Washington, D.C., suburbs after his brother called "expressing concern,"
the police department said in a statement.
Specifics on the call were unclear, but authorities said it was medically related.
"They knocked on the door and received no answer so they began to force entry so they could render care," said Benjamin Barksdale, assistant fire chief for Prince George's County Fire Department.
"As they were forcing entry, several shots were fired from the house through the door, striking two fire department personnel."
Firefighter John Ulmschneider, 39, was killed, authorities said.
Kevin Swain, a 19-year-old volunteer firefighter, was shot four times and is in serious condition
, police said. He is expected to survive.
The brother who called 911 was standing outside the house and also was shot, but his injuries are not life-threatening, authorities said.
Police did not provide the man's name. The Washington Post reported
that he was 61 and that his brother feared the man had suffered a blackout or seizure.
Ulmschneider was a paramedic and 13-year veteran of the county's emergency medical services. He was married and had a 2-year-old daughter, fire department spokesman Mark Brady said.
"This is a day that we have all dreaded in our minds," the Prince George's County Professional Fire Fighters & Paramedics Association said on its Facebook page
"We are keenly aware of the dangers of our profession but we have hoped that God would continue to watch over and protect our members. Now that tragedy has stricken us, we must stand strong and band together to support (Ulmschneider's) family and those who are closest to him."