TAMPA, Fla. (WFLA) — A litany of “concerning” manifestos were found in the home of a Tampa man who admitted to committing murder under an overpass early Sunday morning, according to authorities.

The Tampa Police Department said 30-year-old Timothy McGovern, of Tampa, was the subject of a “detailed investigation” that began on Nov. 6 when a man was shot and killed under an overpass at Hillsborough Avenue and Dale Mabry highway.

When officers arrived at the scene, they immediately began speaking with witnesses who shared what they saw and heard. Gun casings were also found at the scene.

When the 9mm bullet casings were entered into a national database that compares them to other potential crimes, officers said a link was made to an unrelated incident that took place along Bayshore Boulevard roughly four hours before the murder.

In that case, authorities said an unidentified white man, later identified as McGovern, fired a gun into the water. A witness told police that McGovern told her, “there’s my target” before he pulled the gun from his waistband and fired into the water.

“Thankfully, no one was struck by a bullet in this case,” officers said. “And even if shooting into water may not seem like a big deal, these citizens gave us the crucial link to solving the homicide.”

After the casing connection was made, homicide detectives and plain-clothed officers met and formulated a surveillance plan around the city.

On Tuesday night, a Tampa Police officer spotted McGovern riding his bicycle along West Hillsborough Avenue, less than a mile from the scene of the murder.

When detectives interviewed McGovern, he admitted to firing the gun on Bayshore to “test” it. He also admitted having previous encounters with the murder victim, walking to the underpass on the night of the murder, and setting out to take the victim’s life.

McGovern also told officers he stabbed the victim on July 4.

While the two have had previous encounters, authorities are working to determine the extent of how well they knew each other.

During a search of McGovern’s home, officers said they found the 9mm handgun he used in the murder. The gun had been reloaded. Detectives also found a litany of manifestos.

“What is written in there is concerning,” the department said in a release regarding the discovery.

“I have no doubt that the detailed investigation completed by our detectives and their commitment to finding justice in this – and every case – stopped this person before he could take another life,” Tampa Police Chief Marry O’Connor said.