The case escalated into a major manhunt.
手入れ can mean a police raid or crackdown, but is more general and can also refer to maintenance or care. 大捕物 is specifically a large-scale capture operation.
Standard kanji spelling.
Variant spelling with okurigana; less common but still encountered.
Compound of 大 (おお, 'big, large-scale') and 捕物 (とりもの, 'capture, arrest'). The exact historical derivation is uncertain, but the word is formed from common elements.