Gardai fear a simmering row over the use of "bird bangers" - an audio device to scare birds - triggered the murder of a 74-year-old Kerry farmer with a teleporter machine.
Anthony O'Mahony died when his car was struck side-on by the teleporter, a type of heavy agricultural haulage machine, as he visited his farm outside Ballyduff in north Kerry shortly before 9am yesterday.
His brother, Seamas, said the family was "totally heartbroken".
He stressed that there was no inkling that his brother was under any kind of threat or in danger.
"We don't know - we thought at the start he was involved in an accident, that's all," he said.
"We used to have a bird banger on below there. Some people don't like to hear that going.
"That's the only thing. He would go down there and turn it on at 8am and then turn it off again at 8pm. It was nothing out of the ordinary.
"But no, he absolutely was not living in fear."
Mr O'Mahony heard the news of his brother's death as he was travelling in connection with his pre-cast concrete business.
"His wife, Margaret, rang me at 10.30am and told me there was a bad accident over in Rattoo," he said.
"It's been very, very difficult. Anthony was very quiet but very knowledgeable. He was totally dedicated to his work. If he could do a good turn for someone he would do it."
He said he last spoke with his brother on Saturday.
Mr O'Mahony, who was single and unmarried, died at the scene at Rattoo despite efforts by local GPs and paramedics to save him.
While he farmed a holding at Rattoo, he lived around 3km away on the other side of Ballyduff village.
He is understood to have suffered catastrophic injuries to his head and torso in the impact between his car and the teleporter which had a pronged extension used for lifting heavy loads. Part of the large wheels of the machine also mounted Mr O'Mahony's car.
The collision happened just 100 metres from a local GP surgery.
A man in his 60s, who was known to Mr O'Mahony, was arrested at the scene and taken to Listowel Garda Station for questioning.
He can be held for an initial period of 24 hours.
By 11am, gardai had launched a murder investigation.
Officers sealed off the narrow country roadway, 2km from Ballyduff village, to allow for an examination by Garda Technical Bureau investigators.
Uniformed gardai also began door-to-door enquiries to determine if anyone had witnessed the fatal collision.
Mr O'Mahony's body remained at the scene until it could be examined by assistant state pathologist Dr Margaret Bolster.
The body was then transferred to Tralee for a post- mortem examination shortly before 7pm.
Gardai must decide later today whether to release the man in custody or to charge him.
Supt Dan Keane appealed to anyone with information to contact Listowel Garda Station.
Supt Keane confirmed that both the deceased and the man in custody were known to each other.
"We would appeal to anyone who may have information or who may have witnessed what happened to contact us," he said.
"This has been a huge shock for the area."
Retired local teacher Maurice O'Connor knew Mr O'Mahony and described him as "a lovely man".
"Anthony was a perfectionist in everything he did," he said.
"He was only in the post office a couple of weeks ago and I had a chat with him. He was talking about the season ahead."