regular past tense, following the stem "e" - "a" rule (with the regular exception of masc. pers. plurals)
"Verbs with infinitives in -e change e to a in all forms except the masculine personal plural."
Swan, Oscar (2008-10-12). Polish Verbs Essentials of Grammar, Second Edition (Verbs and Essentials of Grammar Series) (Kindle Locations 1339-1340). McGraw-Hill Education. Kindle Edition.