It's a yes
Just one word 'Hypnotism' and things started to make sense. Suyin knew the serious side-effects of hypnosis if done with malicious intentions and under wrongful practice. Using hypnosis repeatedly ultimately weakens the mental state of an individual, destroying the very essence. No doubt Zeng's personality changed so much over a period of time.
She recalled something, "The phone call?"
"Yes, probably it was the phone call." Wang Shi answered, "We get it checked, the call lasted barely ten seconds. The number is issued under a fake identity and it's not reachable now, probably disposed,"
"And... before you ask, the reason your brother behaved violently was because of me." Suyin and Wang Shi both frowned at Dr. Jeff, scaring the old man. "Hold it. Hold it. I have done nothing wrong. Let me explain...."