A day after announcing that a 911 caller had claimed responsibility for a string of highway shootings, investigators said Saturday that a second man has stepped forward and threatened to attack police officers.

Investigators say they believe the man who called early Saturday morning is different from the man who repeatedly called 911 on Monday to claim responsibility for 20 shootings at cars, school buses and homes on or near a section of Interstate 270 (search) south of the city. One person was killed in November.

"It's gonna get worse," the latest caller said. "I intend to start shooting at the police now."

Sheriff's officials said they warned law enforcement officials around the state of the latest caller's threats, and that a task force on the shootings was taking both sets of calls seriously.

Sheriff's officials issued a press statement and released a tape of the roughly 50-second call on Saturday, but did not immediately respond to requests for more information.

On the tape, the caller sounds like he has a deep voice, and says he was committing the shootings because the police have "corrupted the world."

He tells the dispatcher, "Tomorrow, the whole world will see our highways."

"They will?" the dispatcher asks.

The caller responds, "They will see my impact. Tomorrow, live."

Authorities also are investigating the first caller, who made four 911 calls Monday totaling about a minute and said, "I'm the highway shooter."

The man said he fired at a car that day but did not specifically claim responsibility for any of the shootings connected by police. Police had no reports of highway shootings Monday.

The police dispatcher appears to dismiss the first caller on the 911 tape, saying "whatever" several times and "Yeah, yeah, yeah." At another point she says, "You just want attention, don't you."

The call ends soon after she asks the caller to stay on the line while the call is traced.

Police were investigating the dispatcher who took Monday's calls. Police spokeswoman Sherry Mercurio said the dispatcher's use of words such as "whatever" was inappropriate.

The shootings began in May, but most have occurred since October. The only person hit, Gail Knisley (search), 62, was fatally wounded Nov. 25 while riding in a car on I-270.

The last shooting linked to the case took place Jan. 22, when a car was hit on Interstate 71 (search), which intersects I-270.