Final answer:
Laocoon, a Trojan priest of Poseidon, was the first Greek man to leap ashore at Troy. He was killed when Athena or Poseidon sent two sea serpents to torture and kill him and his two sons.
Step-by-step explanation:
The first Greek man to leap ashore at Troy and was killed was Laocoon.
Laocoon was a Trojan priest of Poseidon who warned the Trojans about the Greeks leaving a large wooden horse at the gates of Troy. Unfortunately, Athena or Poseidon, upset by his warning, sent two sea serpents to torture and kill Laocoon and his two sons.