וְאִם־בְּפֶ֥תַע בְּלֹא־אֵיבָ֖ה הֲדָפ֑וֹ אוֹ־הִשְׁלִ֥יךְ עָלָ֛יו כָּל־כְּלִ֖י בְּלֹ֥א צְדִיָּֽה׃
Ngunit kung bigla niya siyang itinulak nang walang pagkakaaway, o hinagisan niya siya ng anumang kasangkapan nang hindi nakaabang sa kanya,
Rashi
בפתע means BY ACCIDENT. In the Targum it is translated by בתכיף (in close proximity), meaning that he was very close to him and so had no time to be careful about him (i.e. to be on his guard not to kill him; see Rashi on Makkot 7b).
Avi Ezer
And not an enemy to him. It is explained that it is a light language standing on the pattern of "Vayehi," as in "Vayehi Sha'ul Ovin et David" (And Saul was hostile to David). And it is not appropriate in terms of linguistic precision to say that it is a name indicating possession, as in "Ein Damim Lo" (He has no blood).
Rabbeinu Bahya
ואם בפתע בלא איבה, “But if with suddenness, without enmity,” The word “suddenly” means that it was caused by an accident. The victim was close by the killer and he did not have a chance to be warned.