JITL Day 16 VLAN Lab unexpected behavior?

I finished the JITL VLANs (Part 1) Day 16 Lab (https://www.youtube.com/watch?v=-tq7f3xtyLQ) and everything worked fine. However, experimenting further, I pinged the broadcast address 10.0.0.127 of the second subnet from PC1 (10.0.0.1, first subnet and VLAN 10) and unexpectedly received ICMP Echo Replies from the router's g0/0 interface (10.0.0.62, VLAN 10, and is PC1's gateway). Can someone please explain this behavior? Thanks in advance!