How to make projectile face direction of where it's traveling?

The script below fires an arrow from a crossbow, but the arrow doesn't face the way it's traveling. Does anyone know how to fix it?

tool = script.Parent
plr = game.Players.LocalPlayer
mouse = plr:GetMouse()

tool.Equipped:Connect(function()
    mouse.Button1Down:Connect(function()
    local p = Instance.new("Part", workspace)
    p.CanCollide = false
    p.Size = Vector3.new(1,1,1)
    p.Position = tool.Handle.Position
    tool.Mesh:Clone().Parent = p
    local bv = Instance.new("BodyVelocity", p)
    bv.Velocity = mouse.Hit.lookVector * 100
    end)
end)