SÅ«ta said: Hearing the words of the Lord, Arjuna the slayer of hostile warriors, performing Äcamana, circumabulated Kṛṣṇa and aimed his brahmÄstra in order to counteract AÅ›vatthÄmÄ’s weapon.
Purport
Tam refers to Krsna. For destroying Asvatthama’s weapon (brahmaya) he aimed his weapon.