He can be found dead along with multiple other Pack members in the random encounter Dead Pack + Deathclaw. On his body there is a holotape named "The Test", on which he describes how he will become the new Pack Alpha after bringing the head of a deathclaw to Mason.
|Apparel||Weapon||Other items||On death|
|Raider armor||The Test|
Weylan is appears only in Fallout 4.