TAMPA — In the weeks that a Tampa neighborhood lived in fear of a serial killer, an iPhone owned by Howell Emanuel Donaldson III ran Google searches for the phrase "Seminole Heights killer."

The phone's web history included visits to the Twitter and YouTube pages of the Tampa Police Department, where officials posted videos and other information about the search for the person responsible for four random shootings.

Those are among the details included in a search warrant affidavit in the state's case against Donaldson, who is charged with first-degree murder in the deaths of Benjamin Mitchell, Monica Hoffa, Anthony Naiboa, and Ronald Felton. The slayings terrorized the southeast Seminole Heights neighborhood and drew international attention as police hunted a murderer.

BACKSTORY Complete coverage of the Seminole Heights killings

The Hillsborough State Attorney's Office released the affidavit Friday, along with inventories of data and other evidence seized as part of the investigation.

The documents include several other revelations:

• An agent with the federal bureau of Alcohol, Tobacco, Firearms and Explosives sent a text message to Donaldson on Nov. 1, in the midst of the killings, asking him about his purchase of a Glock .40-caliber handgun weeks earlier from a Shooter's World store. The text went unanswered, the affidavit says.

• Donaldson's phone recorded multiple visits to specific web sites a few hours after each of the first three shootings. The names of those web sites have been redacted from the affidavit at the request of Donaldson's defense attorneys.

• On the day of his arrest, Donaldson's phone recorded web searches and other activity related to airplane flights.

The investigation reached a dramatic climax Nov. 28, when Delonda Walker, a manager at a McDonald's in Ybor City, flagged down a police officer inside the restaurant.

In a panic, Walker explained that Donaldson, her co-worker, had handed her a plastic bag that contained a gun, according to the affidavit. She said Donaldson told her he was going to a nearby Amscot store to collect all his money and "get out of town."

Minutes later, Donaldson's Ford Mustang appeared in the parking lot.

"He's here! He's here!" Walker said.

Officers detained Donaldson, who let them search his car and phone. He later agreed to be interviewed at Tampa police headquarters.

In the meantime, the .40-caliber handgun was sent to the Florida Department of Law Enforcement for forensic tests. Results hours later showed it was the same gun that fired bullets in all four killings.

The affidavit details each of the brutal slayings and the subsequent police response.

None of the victims had any property taken from them. All except Naiboa were shot multiple times. Silver bullet casings, marked "SIG 40, S & W," were found on the ground at each of the shooting scenes.

Donaldson told detectives he bought the firearm from Shooter's World, a fact confirmed by an Oct. 3 purchase receipt, which recorded payment of $399. A second receipt from three days later showed Donaldson bought a 20-round box of .40-caliber ammunition.

He claimed he was unfamiliar with the Seminole Heights neighborhood, according to the affidavit. But data lifted from his phone showed it had been close to the crime scenes at about the time the shootings occurred.

Police pulled location and usage data related to at least six applications on Donaldson's phone. They included Facebook, Uber, Snapchat, Instagram, and the iPhone weather application, run by weather.com.

A day after Donaldson's arrest, detectives interviewed a witness who told them Donaldson spent the night of Nov. 13 at her home on S West Shore Boulevard. Sometime that night, he left, but returned to the West Shore address in the early morning hours.

The witness, identified as Nicole Minnis, said she remembered the visit because she had several missed phone calls from Donaldson early that morning. She figured he was locked out of her house.

Cell phone records showed three calls from Donaldson to Minnis at 5:16 a.m. and 5:17 a.m. that morning. Less than a half hour earlier, Ronald Felton was shot to death on Nebraska Avenue.

Donaldson, 25, has been jailed without bail since his arrest.

While the documents released Friday shed new light on the high-profile murder case, many questions remain. Chief among them: why?

Police and prosecutors have yet to detail a possible motive for the murders. Additional investigative records might be released as soon as next month.

Prosecutors have declared their intent to seek the death penalty if Donaldson is convicted at trial.

Earlier this week, his lawyers requested that he undergo a psychological examination to determine if he is mentally ill. Circuit Judge Mark Wolfe approved the appointment of Dr. Richard Carpenter to conduct the mental assessment. The doctor's report is due by the end of May.

Contact Dan Sullivan at dsullivan@tampabay.com or (813) 226-3386. Follow @TimesDan.