Upon hearing this omen from the sky, he (Kamsa) caught hold of his sister's (Devaki) hair with his left hand and took up his sword with his right hand to sever her head from her body - SB 10.1.35

Expressions researched:
"upon hearing this omen from the sky, he caught hold of his sister's hair with his left hand and took up his sword with his right hand to sever her head from her body"

SB Canto 10.1 to 10.13

Kaṁsa was a condemned personality in the Bhoja dynasty because he was envious and sinful. Therefore, upon hearing this omen from the sky, he caught hold of his sister's hair with his left hand and took up his sword with his right hand to sever her head from her body.

SB 10.1.35, Translation and Purport:

Kaṁsa was a condemned personality in the Bhoja dynasty because he was envious and sinful. Therefore, upon hearing this omen from the sky, he caught hold of his sister's hair with his left hand and took up his sword with his right hand to sever her head from her body.

Kaṁsa was driving the chariot and controlling the reins with his left hand, but as soon as he heard the omen that his sister's eighth child would kill him, he gave up the reins, caught hold of his sister's hair, and with his right hand took up a sword to kill her. Before, he had been so affectionate that he was acting as his sister's chariot driver, but as soon as he heard that his self-interest or his life was at risk, he forgot all affection for her and immediately became a great enemy. This is the nature of demons. No one should trust a demon, despite any amount of affection. Aside from this, a king, a politician or a woman cannot be trusted, since they can do anything abominable for their personal interest. Cāṇakya Paṇḍita therefore says, viśvāso naiva kartavyaḥ strīṣu rāja-kuleṣu ca.