A 34-year-old man has been arrested in connection with the stabbing death of a 79-year-old motorist in West Sussex.
Armed officers arrested the suspect, from Worthing, at around 2pm on Friday.
Video footage showed paramedics treating the grandfather at the side of the road.
An air ambulance also landed nearby and the crew took over Mr Lock’s treatment, but he died at the scene.
Mr Lock’s grandson, Ashley Goodlad, posted on Facebook: “He was the kindest, softest and most generous man you could ever wish to meet, it’s just so confusing right now just trying to work out an answer for why this has happened.”
John Lucas, a long-time friend, said he had known Mr Lock for more than 50 years.
He said: “It’s such a terrible thing. He was an unbelievable guy. He would do anything for anyone.”
Adrian Palmer, secretary of Worthing Excelsior Cycling Club of which Mr Lock was a longstanding member, said: “Don Lock was a kind, gentle and fair man and a good friend.
“He was a key member of Worthing Excelsior Cycling Club for about 50 years and served the club well in many different roles.
“His death is an irreplaceable loss to the club and our thoughts are with his family, to whom the club will offer our total support at this tragic time.”
A witness described on Facebook seeing an elderly lady with the injured man in an ambulance at the scene. Police have confirmed the victim was travelling alone when he was stabbed.
A card on flowers left at the scene read: “I have lost a very special grandad. My only grandad. I love you so much.
“You will be truly missed by so many people. I just wish I could hug you one last time.”