He was killed in a automobile Accident while helping to take two escaped robbery suspects they had just arrested to the jail.
He was driving the suspects car and following the Sheriffs car with the prisoners in it; when a sudden stop slammed the car he was in to the back of the Sheriffs car. He died the next day. Here are the articles I found on the incident.

Howard Gunter is buried in the Van Alstyne Cemetery.

The Whitewright Sun
April 25, 1934
Posseman Killed in Crash (part of the Posse to capture Raymon Hamilton.
Part of the Clyde Barrow Gang. They were arrested in Howe)

"Howard Gunter, assigned to drive the robber's stolen car into Sherman, became involved in an automobile wreck as he reached the business district and was injured fatally, dying in a Sherman Hospital a short time after the accident. Gunter had been one of the men pursuing Hamilton and his companion across Collin County. "
Officers here said Hamilton and his companion would be taken to the county Jail at Dallas for safe-keeping. ..............

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Brownsville Herald
April 26, 1934
This is part of a long article about the arrest of Hamilton.

"The capture of Hamilton accidentally cost the life of Howard Gunter, special deputy, whose skull was fractured in an automobile accident as he was driving the stolen car Hamilton had used in the Lewisville robbery, into Sherman. Gunter had been driving behind a car load of officers, which halted suddenly. Gunter lost control of the machine and crahsed into the car ahead and careened into a roadside railing, being thrown headlong into the pavement. "