He was reacting to the president's controversial comment about directing security operatives to be "ruthless" in dealing with ballot box snatchers who attempt to disrupt the election.
"Anybody who decides to snatch boxes or lead thugs to disturb it, maybe that's the last unlawful action you'll take. I really gave the military and the police order to be ruthless," President Buhari said during his own party's caucus meeting on Monday.
Secondus called the president's comment a "death sentence on all voters of Nigeria" that should not be obeyed by security operatives.
He said, "Nigerians are tired of President Buhari. And of a truth, over three years, killings and killings and now you have ordered that more people should be killed.
"Why do you like blood? I want to ask Buhari, 'Why do you like blood?'
"Why do you want to kill your country men and women. For the sake of election? That you must be a president? You know you are not God. Buhari, I'm addressing you, you know you are not God.
"All your actions in the last three years are against the people of Nigeria: hunger, killings, unemployment; you are not sensitive to it."
He said the PDP will resist any attempts by the ruling All Progressives Congressive (APC) to ensure that the results of the elections will reflect the will of the Nigerian people.
Atiku slams Buhari for comment
While also condemning President Buhari's comment during the Tuesday meeting, the PDP's presidential candidate, Atiku Abubakar, urged security operatives to not carry out any unlawful orders even if they come from the office of the Commander-in-Chief.
"In military, commanders and officers are not bound to execute orders that are manifestly unlawful. This is the law, this is the tradition in the military.
"If you're a professional military commander, officer and soldier, and also a policeman, you're not bound to execute an order that's manifestly unlawful no matter who issues that order," he cautioned.
Atiku and Buhari are favourites to win the 2019 presidential election which was recently rescheduled from its initial February 16 date to February 23.
71 other candidates are listed to contest in the election even though some of them have dropped out and declared support for Atiku or Buhari.
The leading candidates in the chasing pack are Kingsley Moghalu of the Young Progressive Party (YPP), Omoyele Sowore of the African Action Congress (AAC), and Fela Durotoye of the Alliance for New Nigeria (ANN).