Multiple Florida sheriff's offices and police departments are offering condolences to their colleagues in the north Florida county.
Investigators do not know what the shooter's motive was, and Schultz said there are no "indications as to why this tragedy occurred".
He called both deputies "the best of the best".
Gov. Rick Scott in a statement said he and his wife "are heartbroken by the loss of the two law enforcement officers in Trenton".
A construction worker who witnessed the shooting said that Highnote emerged from the restaurant "calm as can be", WFLA reported.
The cops were eating at a Chinese restaurant in the city of Trenton, about 35 miles west of Gainesville, when the shooter walked up and started blasting through a window, officials said in a statement.
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Highnote killed himself in his vehicle shortly after the murder.
Schultz said law enforcement has been "demonized" by "every type of hate", and all his deputies were guilty of was "wanting to protect you and me".
The slain deputies were Sgt. Noel Ramirez and Deputy Taylor Lindsey.
Bill Cervone, the state attorney for Floridas 8th Judicial Circuit, called the act "inexplicable".
Florida Attorney General Pam Bondi issued a statement declaring, "My heart breaks down with the awful information of 2 Gilchrist County deputies that were blindly murdered whilst in front of responsibility".
"It is a true evil for anyone to hurt a law enforcement officer, and in Florida, we have zero tolerance for violence, especially against police", he continued. "We thought this was the best way to bring law enforcement and the community together to honor these men for what they gave".
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Public Health Ministry spokesman Wahid Majro said more than 100 others were wounded by the blast, claimed by the Islamic State. Among the victims of the attack, which the terrorist Daesh group claimed responsibility, were 21 women and five children.
His goal is to hand over a $20,000 check, raised by donations, in honor of the C.O.P.S charity, Concerns of Police Survivors, which raises money for the families of fallen law enforcement officers.
A message from Sheriff Shultz to the citizens of Gilchrist County:I want to ensure everyone here in our Gilchrist...
Other than being cited for making an improper turn back in 2012, Highnote has nothing on his record in Gilchrist County. "And we're very proud of them". The suspect appears to have walked to the front of the business and shot both men without warning.
The shooter has not been named, but Schultz said he was "a lone assailant".
"They just wanted to get something to eat".
Condolences poured in through the afternoon from federal, state and local officials and agencies, including President Donald Trump.
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Under current federal laws, the minimum age to buy a handgun from a licensed dealer is 21. This includes a friend, online buyer or seller at a gun show, The Hill reported.