Kinslaying at Alqualondë
Then the Noldor drew swords, and the Teleri their bows, and there was a bitter fight that seemed evenly matched, until the second Host of the Ñoldor, led by Fingon, arrived together with some of Fingolfin's people. Misunderstanding the situation, they assumed the Teleri had attacked the Ñoldor under orders of the Valar, and they joined the fight. In the end many Teleri were slain and the ships taken. All that continued towards Middle-earth were therefore cursed by Mandos.
The Sack of Doriath where Dior Eluchíl was killed by the Sons of Fëanor is referred to as the Second Kinslaying in The Silmarillion, and the attack by the Sons of Fëanor on the Mouths of Sirion where Elwing was attacked is called the Third Kinslaying. It was stated by Eönwë herald of Manwë that because of these evil deeds the remaining Sons of Fëanor had lost all right to the Silmarils.