Police are investigating whether motorcyclists were speeding when they crashed into a van yesterday in Kailua.

One motorcyclist, a 46-year-old Pearl City man, died at Castle Medical Center.

The other, in his 40s, was taken to the Queen's Medical Center in critical condition after the accident, which occurred at about 2:10 p.m.

The motorcyclists, riding in a group of five, rear-ended a van as it tried to make a U-turn around a median on Kailua Road where U-turns are allowed.

Police said the van, driven by a tourist from Japan, was heading toward Kailua when it crossed from the right lane to the left to make the turn.

Outside a 7-Eleven near the accident scene, Lucinda Goldstein and her husband, Mark Nunes, heard a skid, then a boom.

Goldstein ran into the store to call for help, and her husband rushed to the scene.

“;I seen one guy, he was almost under the van,”; said Nunes, of Waimanalo. “;I think he was dead on impact.”;

He tried to help the injured motorcyclist, who was conscious and trying to walk.

“;His whole right leg, from the knee down, shattered,”; Nunes said. “;I tried to keep him on the ground, keep him calm.”;

Nunes said two adults and two children in the van “;were real shaken up.”;

Police closed the Kailua-bound lanes of Kailua Road from Kalanianaole Highway for about three hours to investigate. Neither biker was wearing a helmet, police said.